Ping isn't really the issue here. It boils down to tick rate and throttling performance to keep server loads and costs in check.
SE have historically always been super cautious on all aspects of the infrastructure behind their MMOs:
Remember how unsubbing for a period of time in FFXI would get your character data literally removed from the live servers and swapped to cold storage? You had to contact them and politely ask to have your character manually restored originally.
FFXIV has always had a slow GCD and tick rate, both means to significantly lower CPU load. Another area where they saved server CPU cycles was launching the game with comical levels of client trust.
Memory usage? IMHO that's one of the real reasons we don't get a proper glamour log style system. It would require the addition of several extra data arrays per character, adding to the footprint noticeably when you're talking a few hundred characters per zone.
In WoW I had a better experience PvPing with ~200ms latency from the UK to US west coast servers. I PvP'd pretty much exclusively through Vanilla and BC to the highest level and had no problems whatsoever. It was only when WotLK and Arena landed that the ping gave me problems and that was specifically down to the amount of precision needed to pillar block long enough to get out of combat drinking in. No rubber banding, things didn't hit me when it felt like they shouldn't. I had no problems grounding pom pyros etc.
FFXIV PvP is just a lower quality experience all round because SE aren't willing to foot the bill on the backend with a faster update rate.